問題描述

誰能告訴我為什么這不起作用?

Can anyone tell me why this isn't working?

>>> import mock
>>> @mock.patch('datetime.date.today')
... def today(cls):
...  return date(2010, 1, 1)
...
>>> from datetime import date
>>> date.today()
datetime.date(2010, 12, 19)

也許有人可以提出更好的方法?

Perhaps someone could suggest a better way?

推薦答案

有幾個問題.

首先，您使用 mock.patch 的方式不太正確.當(dāng)用作裝飾器時，它僅在裝飾函數(shù)內(nèi)將給定的函數(shù)/類(在本例中為 datetime.date.today)替換為 Mock 對象.所以，只有在你的 today() 中，datetime.date.today 才會是一個不同的函數(shù)，這似乎不是你想要的.

First of all, the way you're using mock.patch isn't quite right. When used as a decorator, it replaces the given function/class (in this case, datetime.date.today) with a Mock object only within the decorated function. So, only within your today() will datetime.date.today be a different function, which doesn't appear to be what you want.

你真正想要的似乎更像是這樣的:

What you really want seems to be more like this:

@mock.patch('datetime.date.today')
def test():
    datetime.date.today.return_value = date(2010, 1, 1)
    print datetime.date.today()

很遺憾，這行不通:

>>> test()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "build/bdist.macosx-10.6-universal/egg/mock.py", line 557, in patched
  File "build/bdist.macosx-10.6-universal/egg/mock.py", line 620, in __enter__
TypeError: can't set attributes of built-in/extension type 'datetime.date'

這會失敗，因為 Python 內(nèi)置類型是不可變的 - 請參閱 這個答案了解更多詳情.

This fails because Python built-in types are immutable - see this answer for more details.

在這種情況下，我將自己繼承 datetime.date 并創(chuàng)建正確的函數(shù):

In this case, I would subclass datetime.date myself and create the right function:

import datetime
class NewDate(datetime.date):
    @classmethod
    def today(cls):
        return cls(2010, 1, 1)
datetime.date = NewDate

現(xiàn)在你可以這樣做了:

>>> datetime.date.today()
NewDate(2010, 1, 1)

這篇關(guān)于試圖模擬 datetime.date.today()，但不工作的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網(wǎng)！